Improvement in screens



UNITED STATES P TENT GFFI E.

DAVID G. SMITH, OF (JARBONDALE, AND JOHN B. SMITH, OF DUNMORE, PA.

IMPROVEMENT IN SCREENS.

Specification forming part of Letters Patent No. 179,229, dated J une 27, 1876; application filed May 22, 1876.

To all whom it may concern:

Be it known that we, DAVID G. SMITH, of Garbondale, and JOHN B. SMITH, of Dunmore, both in the county of Luzerne and State of Pennsylvania, have inventedcertain new and useful Improvements in Revolving Screens, specially adapted to the separation of coal from slack; and that the following is a full, clear, and exact description of the same, reference being had to the accompanying drawings, making a part of this specification, in which Figure 1 represents our coal-screen in perspective. Fig. 2 represents the same in trans-. verse vertical section.

Our invention relates to revolving screens used to separate coal from the fine particles of dust or slack mixed with it when preparing it for the market. Cylindrical revolving screens are generally used for that purpose; but a great difficulty is experienced when they are used to separate the dust from the coal known in the market as chestnut or pea sizes, as it is very common at the mines for the coal and small particles to be wet, and so agglomerated that the cylindrical screens, in revolvthrowing the mixture from one of the sides upon the other, and found that, while the broadest sides (such as formed by a triangular or square prism) gave good results in separating dust from small coal in a dry state as it produced the greatest overturning and agitation, it had some disadvantages when operating upon damp or wet small coal and fine slack, as the mixture was thrown into the acute or rectangular angles of the screen, where, the meshes being small, it lodged, and was retained by the centrifugal motion of the screen. We found that the angle between two consecutive sides should be an obtuse angle,

to prevent lodging of the coal-dust, and that the broadest sides produce thegreatestscreening capacity; and our invention is based upon the discovery that a prismatic revolving screen, having the sides of maximum breadth with a minimum number of obtuse angles, re-

sults, practically, in attaining a maximum screening capacity, and reduces to a minimum the cloggmg tendency. In other words, we

have discovered that the outline of the screen cylindrical or other form of heretofore-known screen having the same length and periphery, and using the same power to revolve it.

Our invention consists in a prismatic revolving screen, whose adjacent sides meet at an angle of about one hundred and eight degrees, so as to insure the broadest sides compatible with their meeting at obtuse angles, and the largest effective screening-surface, combined with adequate stirring and spreading of the material within the screen.

In the drawings,.the screen is represented at A. It may be made of sheets of woven wire or of perforated sheetiron, united together and to the frame by bolts passing through longitudinal ribs a, located at the outside of the screen at the angles formed by two consecutive sides of the screen. The screen A and its ribs a are connected to the revolving shaft B by means of radial arms 0, (one for each angle,) located at suitable distances within the screen. One end of each of these arms'is attached to hubs b, mounted upon and securely fastened to the shaft B, while the other end passes through one of the angles and the corresponding rib, to which it is secured by a not or otherwise. The shaft B passes through suitable bearings d, mounted upon supports D D, located at each end of the screen, the support D being higher than the support D, so as to give to the screen the desired inclination. The shaft B, and with it the screen, can be revolved by means of the crank B, by gear-wheels connected with it, or by a belt and pulleys.

We have found that a screen having a perimeter of ten feet, or thereabout, a speed of thirty-five to forty revolutions per minute, and an inclination of its axis such as will cause the material to tra el from the point at which it enters three hundred and eighty to four hundred feet in a spiral course over the inner surface of the screen to the point at which it is discharged, will produce a thoroughly-screened coal under all the conditions under which screening is usually done.

Revolving screens have been made either triangular, quadrangular, or with six or more sides; but that they have been formed pentagonal in cross-section is new and of our in vention.

Having thus fully described our invention, what we claim is- A pentagonal prismatic revolving screen, whose adjacent sides meet at an angle of about one hundred and eight degrees, so as to insure the broadest sides compatible with their meeting at obtuse angles, and the largest effective screening-surface, combined with adequate stirring and spreading of the material, substantially as described DAVID G. SMITH. Witnesses: JOHN B. SMITH.

J OHN STUART,

E. E. MASSON, LEwIsS. WATERS, W. R. EDELEN. 

